Viscose spinning



United States Patent 3,116,352 VKSCOSE ESPENNTNG Paul V. Brewer, Elizabethton, Tenn, assignor, by mesne assignments, to lleaunit Corporation, a corporation of New Yorlt No Drawing. Filed May 2, 1957, Ser. No. 656,483 Claims. (Cl. 264-189) This invention relates to an improved cellulose Xanthate spinning solution and to an improved method for producing high-tenacity regenerated cellulose products, especially yarn suitable for use in automobile tires, etc, from this improved spinning solution, and to the resulting products.

High-tenacity viscose rayon is usually produced by spinning viscose in an acid-salt bath containing, in addition to sodium sulfate and sometimes magnesium sulfate, a zinc salt (see U.S. Patents No. 2,312,152 and No. 2,324,437), and stretching the freshly coagulated thread in a second hot water bath containing small amounts of acid and salt as described in U.S. Patent No. 2,192,074.

As is well-known in the art, viscose composition, viscose ripeness, spin bath composition, and spin bath temperature must each be adjusted and correlated with one another to yield yarn having the most favorable physical properties, i.e., tensile strength, elongation, fatigue, heat stability, etc. In tire yarn, fatigue and heat stability are even more important than tensile strength. The elongation value of tire yarn should be less than that usually desired in textile yarn, and the loss in strength in plying and cabling should be low.

In response to consumer demand the viscose rayon producers have searched constantly for methods for further improving the physical properties of high tenacity yarn. Increasing the zinc sulfate content of the spin bath gives an improved yarn, but eventually a point is reached Where more zinc sulfate has but little further effect on the yarn properties. Another approach has been to add to the viscose, to the spin bath, or to both, various spinning modifiers.

Some investigators hold that the cellulose pulp (from cotton or Wood) used in the production of high tenacity viscose rayon should contain only small amounts of very low molecular Weight materials (dp. 75 or less) and that the cellulose chains in the pulp should have a uniform molecular weight, rather than a high average molecular weight with some very high molecular Weight chains and some low molecular weight chains (see, for example, TAPPI, volume 39, No. 1, pages 24-2248, April 1956, and Paper Trade Journal, September 3, 1956, pages 2125). A carefully prepared Wood pulp, containing only a minimum amount of very low molecular weight material, and having a uniform cellulose chain molecular weight distribution, is said to be just as satisfactory for the production of high tenacity viscose rayon as cotton pulp. The wood pulp sold by Rayonier, Inc. under the designation Cordenier J is an example of such a pulp. Gthers hold that when producing viscose for high tenacity yarn care should be taken that the cellulose chains in the high quality (high molecular weight) pulps, preferably cotton pulp, are broken down only as much as is necessary to obtain the optimum spinning viscosity, and that the amount of low molecular weight cellulose chains is not greatly increased. The importance of these latter factors in the production of high tenacity yarn has been brought out by specific disclosures in the patent art (see, for example, U.S. Patents No. 2,586,796, No. 2,592,355, and No. 2,732,279, and German Patent No. 838,936). Still others find it possible to produce high tenacity viscose rayon from wood pulp of comparatively low average molecular Weight containing considerable very low molecular weight material. This is accomplished by reducing the alkali cellulose ageing time and/or temperature, or by eliminating the ageing step completely, to avoid any considerable further degradation of the cellulose chains. Much of the very low molecular weight material is removed from such pulps by the dip lye.

The yarn properties are also improved if green, i.e., substantially unripened, viscose is spun at a high salt point (see, for example, U.S. Patents No. 2,581,835 and No. 2,598,834).

Despite the improvements resulting from these and other efforts, the consumers of high-tenacity yarn have demanded still further improvements.

1 have found, unexpectedly, that high-tenacity viscose rayon having improved physical properties, especially tensile strength and fatigue, may be obtained by spinning viscose in a zinc containing acid-salt spin bath in the presence of small amounts of a polyalkylene glycol, or a derivative thereof, and one or more soluble hydroxy fatty acids, and preferably hydroxy lower fatty acids having from 2 to about 6 carbon atoms, such as hydroxyacetic acid, lactic acid, etc. The hydroxy group is preferably but not necessarily in alpha positions.

The polyalkylene glycol or derivatives thereof and the hydroxy fatty acid modifiers may be added to the viscose, to the spin bath, or to both viscose and spin bath. Moditiers added to the viscose will gradually accumulate in the spin bath, and therefore the additions to the spin bath may be made taking that factor into account. The most favorable results are obtained if small amounts of the modifiers are dispersed and/ or dissolved in both the viscose and the spin bath, although, if desired, the viscose may contain only the polyallrylene glycol modifier, while the spin bath contains suflicient amounts of both with particular reference to assuring the presence in the spin bath of suflicient hydroxy fatty acid to greatly retard tl e degradation of the polyalkylene glycol component as Will be pointed out hereinafter.

While my modifiers are ellective in the various conventional viscoses having different salt points or maturities, I have found that the greatest improvement is obtained by spinning viscose at a salt point of about 7.5 to about 9.0 or more (the salt point is the percent concentration of a sodium chloride solution whi h just coagulates a drop of the viscose; see, e.g., Charles Doree, The Methods of Cellulose Chemistry, 1933, page 254) in an acid-salt bath containing about 4% to about 8% or more, of an appropriate soluble zinc salt such as, in the case of sulfuric acid-containing spin baths, zinc sulfate. The viscose is preferably green or substantially unmatured. High salt point (high maturity) viscose may be obtained, as those skilled in the art will recognize, by various expedients, as by increasing the amount of carbon bisulfide used in xanthation, by reducing the ripening or m"- turing temperature, or by using both expedients, by adding sodium sulfite to the viscose, etc. My modifiers are effective when used with viscose made from the various types of cotton pulps and wood pulps disclosed above.

I am aware that the viscose rayon spinning assistant art discloses the addition of polyalkylene oxides or glycols, or their other or ester derivatives, to cellulose pulp or to alkali cellulose (see U.S. Patents No. 2,362,217, No. 2,392,103, No. 2,393,817, No. 2,423,469, No. 2,481,693, No. 2,623,875, No. 2,710,861, etc.) to viscose (U.S. Patents No. 2,359,750, No. 2,397,338, No. 2,442,331, No. 2,519,227, No. 2,572,217, and No. 2,664,360 and British Patents No. 541,099, and No. 557,218, etc.) and to spin bath (see U.S. Patents No. 2,359,749, No. 2,442,331, No. 2,489,310, etc). I am also aware that the prior art discloses the addition of water-soluble hydroxy fatty acids to viscose (see British Patent No. 309,147, German Patent No. 283,286, etc.) and to spin bath (see U.S. Patents No. 1,102,237, No. 1,376,672, and No. 2,393,199, and German Patent No. 283,286, etc), but I am not aware of any disclosure of the use of soluble hydroxy fatty acids in viscose spinning to enhance the beneficial efiects of the polyalkylene oxides or glycols and their ether and ester derivatives.

It is not entirely clear how hydroxy fatty acids act to enhance the beneficial effects of the polyalkylene glycoltype modifiers in viscose spinning. While factors still unknown to me may also be responsible, I have established that the improved results are, at least in part, due to the fact that the hydroxy fatty acid acts as a preservative for the glycol polymer in the hot acid coagulating bath. Also, the sodium salt formed when the hydroxy fatty acid is added to viscose exerts a coagulating effect on the viscose and a buffering action against the strong acid of the spin bath. Both effects favor the improvement of the yarn properties. My polyalkylene glycoltype modifiers are effective only if their average molecular weight is about 400 or more. These compounds are so sensitive to acid and to elevated bath temperatures that in the absence of a hydroxy fatty acid in accordance with the invention a polyalkylene glycol having an average molecular weight of about 3300 is quickly degraded by the hot acid of a conventional spin bath to an average molecular weight of as low as about 350. It will be understood that a polyalkylene glycol becomes less effective, and finally completely ineffective as a spinning modifier, as its molecular weight drops. The addition of a small amount of a water-soluble hydroxy fatty acid retards this degradation in otherwise conventional viscose spinning so that the average molecular Weight of a polyalkylene glycol falls, for example, from about 3300 to no more than to about 900 to 1100. If a sufficient amount of hydroxy fatty acid is not present in the spin bath, in an extended run the physical properties of the yarn decline steadily from the high values for yarn spun in fresh spin bath containing undegraded polyalkylene glycol modifier. It appears that in order to derive the fullest possible benefit from the synergistic effect of the hydroxy fatty acid it is necessary to have present in a spin bath, either by direct addition or by carry-over from the viscose or both, a certain minimum amount thereof, as will be described more fully hereinafter.

Carbowax 4000, a Carbide and Carbon Chemical Co. polyalkylene glycol having an average molecular weight of about 3300 is a preferred modifier. Lower molecular weight products can be used if the average molecular Weight of the modifier in the spin bath does not fall below about 400, preferably not below about 1000, and products having an average molecular weight of up to about 7,500 are effective. The very high molecular weight polyalkylene glycols, for example, Carbowax 20,000, which should not be degraded to the potentially dangerous point of about 400 average molecular weight as rapidly as Carbowax 4000, are not particularly efficient modifiers, in part, at least, because these higher molecular weight compounds are removed from the spin bath quite rapidly by the yarn and the spin bath filter. As previously stated, my modifiers are most effective when they are dispersed and/ or dissolved in both the viscose and the spin bath, it being especially important that both be dispersed and/or dissolved in the spin bath. The enhancing action of my hydroxy fatty acid modifier makes possible the efficient use of a medium molecular weight alkylene glycol polymer modifier in spin bath.

It is, therefore, an object of the present invention to provide an improved method for producing regenerated cellulose products, such as yarn, ribbon, film, etc., from viscose.

Another object is to provide an improved method for spinning high tenacity viscose rayon.

A further object is to provide an improved zinc-acidsalt type coagulating bath for the production of high tenacity yarn from viscose.

Still another object is to provide an improved method for spinning high salt point viscose.

Yet another object is to provide an improved method for spinning green viscose.

Still other objects are to provide novel and improved viscose compositions as well as improved regenerated cellulose products having commercially more desirable physical properties, especially in regard to fatigue and strength characteristics.

The following examples illustrate various methods of applying the principles of the invention.

EXAMPLES 1-7 Conventional viscose spinning solutions containing about 7.0% cellulose and about 6.0% alkali, calculated as NaOH, were prepared by the well-known methods from a wood pulp sold by Industrial Cellulose Co., Ltd, under the designation SK Tenacell, using about /2% CS based on the cellulose present in the alkali cellulose. When the xanthate crumbs were dissolved in lye to form the spinning solutions, Carbowax 4000" (a Carbide and Carbon Chemical Co. polyethylene glycol having an average molecular weight of about 3300) and varying amounts of hydroxyacetic acid were added. The percent of modifier addition given in Table 1 is based on cellulose in alkali cellulose.

These viscose spinning solutions were converted into 1650 denier tire yarn containing 720 filaments by extruding them at salt point about 8.6 and ball fall viscosity about in a conventional continuous spinning process, including a separate hot acid regeneration step, through spinnerettes having run holes into spin baths at about 67 C. containing about 100* g./l. H 215 g./l. Na SO and 100 g./l.ZnSO and Carbowax 4000 and hydroxyacetic acid as indicated in Table 1.

The freshly extruded threads were drawn about 14 inches through the spin bath in a vertical direction, and were then subjected to a net stretch of about 80% and taken up at about 50 meters per minute. The yarns were washed, after-treated and dried as is usual in the production of such yarn.

Table 1 Viscose Spin Bath Example N o. Carbowax IIydroxy- Garbowax Hydroxy- 4000, acetic 4000, acetic Percent Acid, Percent Acid,

Percent Percent The conventional strength, elongation and fatigue tests were made on the singles yarns and on 11.5/ 10 cable construction. (The 11.5/ 10 cable construction has 11.5 turns per inch Z ply twist, and 10 turns per inch S cable twist.) The data for the seven yarns are given in Tables 2 and 3. The expressions conditioned strength and conditioned breaking elongation refer to yarn having 12% moisture regain. The oven-dry cable strength value is determined on a cable dried overnight in an oven at C. and tested while the moisture regain is still less than 1%.

5 Table 2 PHYSICAL DATA FOR SINGLES 6 Table 5 PHYSICAL DATA FOR SINGLES Strength Breaking Strength Breaking Elongation 5 elongation Yarn From Wet/Dry Yarn from Ex- W Example l\'o. 1'1 atio ample No. ratio Qon- Wet, Con- Wet, Condi- Condi- Wet, ditioned, g./d. (litioned, Percent tioned, Wet, gJd. tioned, percent g./d. Percent g./d. percent Table 6 Table 3 n 0 LD FOR 0 BL S JIYSl A AlA 11.510 A E PHYSICAL DATA FOR 11.5/10.0 CABLES Strength Condi- Strength Qondrtioncd Strength a tioned Strength Yarn breaking lost in from I Breaking Lost in from E:(- Conditioned Oven-dry elongacabling, Fatigue Example Conditioned Oven-Dry Elonga- Cabling, Fatigue ample No. tion, percent No. Ption, t Percent percent ercen d. lbs. (1. lbs. g./(l lbs. g./d. lbs. M

Yarn spun in a freshly prepared spin bath containing Yarn spun in a freshly prepared spin bath containing un degraded Carbowax 4000 but without hydroxy fatty acid had a fatigue value of 67. As spinning was continned, and the poly-alkylene glycol became degraded, the fatigue values fell off rapidly to about 50. This latter value is obtained in normal plant operation when the spin bath is recirculated, regenerated and reused. T lie fatigue values for yarns from Examples Nos. 6 and 7 did not fall 011 as spinning was continued. These fatigue values are obtained in normal plant operation using a recirculated and regenerated spin bath containing both modifiers in the amounts stated.

EXAMPLES 8-13 Viscose spinning solution containing about 7.0% cellu lose and about 6.0% alkali, calculated as NaOH, and about 0.275% Carbowax 4000, based on cellulose in alkali cellulose, was prepared by the method of Examples 1-7, using about 38 /2% CS based on cellulose in alkali cellulose.

This viscose spinning solution was converted into 1650 denier tire yarn containing 720 filaments by extruding it in a conventional continuous spinning process, including a separate hot acid regeneration bath, through spinnerettes having 60 mu holes at salt point about 7.8, and ball fall viscosity about 45, into spin baths at about 67 C. containing about 100 g./l. H 80 215 g./l. Na SO 100 g./l. ZnSO and Carbowax 4000 and hydroxyacetic 'acid as indicated in Table 4. The freshly extruded threads were drawn about 14 inches in a vertical direction through the high Zinc spin bath and were then further processed by a conventional continuous process including the hot acid regeneration bath just mentioned.

The physical data for the yarns thus obtained are given in Tables 5 and 6.

undegraded C'Zll'iTOWtLX 4000 .but without hydroxy fatty acid had a fatigue value of 66. As spinning was continued, and the polyalkylene glycol became degraded, the fatigue values fell off rapidly to about 50. This latter value is obtained in normal plant operation when the spin bath is recirculated, regenerated and reused. The fatigue values far yarns from Examples Nos. 12 and 13 did not fall off as spinning was continued. These fatigue values are obtained in normal plant operation using a recirculated and regenerated spin bath containing both modifiers in the amounts stated.

The addition of as little as about 0.0l25% hydroxyacetic acid to a high zinc spin bath for viscose rayon containing about 0.0050% Carbowax 4000 had a very favorable effect on the physical properties of the yarn, in particular the fatigue values and the singles and cord strengths.

The physical properties of high tenacity yarn, in particular the tensile strength and fatigue, are improved by increasing the alkali content of the viscose, as from about 6.0% NaOH to about 6.5% NaOH, or more, in the approximately 7.0% cellulose viscose disclosed in the examples. However, these high alkali viscoses do not spin well unless the polyalkylene glycol and the hydroxy fatty acid modifiers are used. The use of modifiers in accordance with the present invention thus makes it possible to obtain the further advantages resulting from the use of high alkali viscose.

I have found that to obtain the best yarn properties there should preferably be present in the viscose from about 0.1-1.0% of the polyalkylcne glycol component, based on cellulose in alkali cellulose. Especially good results are obtained when the polyalkylene glycol component is present in the viscose to the extent of about 0.20.35%. With regard the hydroxy fatty acid component I have found that from about 0.l1.0%, based on cellulose in alkali cellulose, may be usefully employed in the viscose, especially good results being obtained when about 0.20-0.40% of the hydroxy fatty acid component is present in the viscose, although as pointed out above all of this component may if desired be be added directly to the spin bath.

From about 0.0020.050% or more of polyalkylene glycol based on the weight of the spin bath should be present in the spin bath, irrespectively of whether by direct addition or by carry-over from the viscose, of both. Particularly desirable results are obtained where this range is about 0.0030.0l0%. The hydroxy fatty acid 7 additive is preferably present to the extent of about 0.01250.050% or more, and preferably about 0.0125- 0.020% based on the weight of the spin bath.

While a polyalkylene glycol having an average molecular weight of about 3,300, such as Carbide and Carbon Chemical Companys Carbowax 4000, is preferred for the practice of this invention, lower molecular weight products may be employed if the average molecular weight of the modifier in the spin bath does not fall below about 400, preferably not below about 1000, and products having an average molecular weight of up to about 7,500 are useful. Ether and ester derivatives of fatty acids having a polyalkylene oxide chain containing at least about 25 ethylene oxide and/or propylene oxide groups are suitable modifiers. The various polyoxyethylene compounds disclosed in US. Patents No. 2,359,749, No. 2,359,750 and No. 2,519,227 are useful modifiers. Where the term polyalkylene glycol is used in the specification or the claims it is intended to include also their ether and ester derivatives, including the hydroxy fatty acid esters, as well as the corresponding polypropylene oxide and mixed polyethylene-polypropylene oxide derivatives.

My modifiers may be incorporated, separately, if desired, in the viscose at any time prior to spinning. This may be accomplished by adding them to the viscose, by incorporating them in the pulp, by adding them to the alkali cellulose, etc. A uniform dispersion of the modifiers in viscose spinning solution is most readily obtained by adding them to the mixer where the cellulose xanthate crumbs are dissolved in lye to form viscose.

I have disclosed the use of my improved spinning process in continuous spinning but it is also useful in spool and pot spinning and it is especially useful in a continuous spinning process, using, for example, the method and the apparatus described in copending application, Serial No. 389,421, filed October 30, 1953, now US. Patent No. 2,898,627.

The process may obviously be modified without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A process for the production of improved cellulosic products which comprises modifying a viscose by incorporating therein a polyalkylene glycol having an average molecular weight of at least about 400 and an hydroxy fatty acid, and extruding the resultant viscose into an acid spin bath.

2. A process for the production of improved cellulosic products which comprises modifying a high maturity viscose by incorporating therein a polyalkylene glycol having an average molecular weight of at least about 400 and an hydroxy fatty acid, and extruding the resultant viscose into an acid spin bath.

3. A process as defined in claim 2 in which the polyalkylene glycol is selected from the group consisting of polyethylene glycol, polypropylene glycol and mixed polyethylene-polypropylene glycols having an average molecu lar weight of from about 400 to about 9,000.

4. A process as defined in claim 3 in which the poly alkylene glycol and the hydroxy fatty acid are both present in the viscose in an amount from about 0.1-1.0% each, based on cellulose in alkali cellulose, and are both present in the spin bath in an amount from about 0.002-

c.) 0.050% and 00125-005070, respectively, based on the weight of the spin bath.

5. A process as defined in claim 3 in which the polyalkylene giycol and the hydroxy fatty acid are both present in the viscose in an amount from about 0.20.35% and 0.200.40%, respectively, based on cellulose in alkali cellulose, and are both present in the spin bath in an amount from about 0.0030.010% and 0.0l250.020%, respectively, based on the weight of the spin bath.

6. A process as defined in claim 3 in which the hydroxy fatty acid contains from 2 to about 6 carbon atoms per molecule.

7. A process as defined in claim 3 in which the viscose has a salt point of about 7.5 to about 9.0.

8. In a process for the production of improved cellulosic products by extruding viscose into an acid spin bath, the improvement which comprises carrying out the extrusion in the presence of additives compressing a polyalkylene glycol having an average molecular weight of at least about 400 and a hydroxy fatty acid.

9. A process as defined in claim 8 in which at least one of said additives is incorporated in the viscose prior to extrusion.

10. A process as defined in claim 8 in which at least one of said additives is incorporated in the spin bath.

11. A viscose solution containing a polyalkylene glycol having an average molecular weight of from about 400 to about 9,000 and a hydroxy fatty acid.

12. A high maturity viscose solution containing a polyalkylene glycol having an average molecular weight of from about 400 to about 9,000 and a hydroxy fatty acid.

13. A high maturity viscose solution having a salt point of about 7.5 to about 9.0 and containing as additives from about 01-10% of polyalkylene glycol having an average molecular weight of from about 1000 to about 7500, and from about 01-10% of a hydroxy fatty acid, both based on cellulose in alkali cellulose.

14. An acid spin bath for regenerating cellulose in the production of extruded products from viscose, comprising a mineral acid, a soluble zinc salt, and additives for improving the regeneration of cellulose from the viscose extruded into said spin bath comprising a polyalkylene glycol having an average molecular weight of from about 400 to about 9000 and a hydroxy fatty acid.

15. An acid spin bath as defined in claim 14 wherein the average molecular weight of the polyalkylene glycol is from about 1000 to about 7500, and the carbon atom content of the hydroxy fatty acid is from 2 to about 6.

References Cited in the file of this patent UNITED STATES PATENTS 1,102,237 Bronnert July 7, 1914 1,955,239 Kampf et al. Apr. 17, 1934 2,324,437 Soukup July 13, 1943 2,593,466 MacLaurin Apr. 22, 1952 2,648,611 Richter Aug. 11, 1953 2,696,423 Dietrich Dec. 7, 1954 2,705,184 Drisch Mar. 29, 1955 2,732,279 Tachikawa Jan. 24, 1956 2,897,178 Hill July 28, 1959 FOREIGN PATENTS 741,727 Great Britain Dec. 14, 1955 763,325 Great Britain Dec. 12, 1956 

1. A PROCESS FOR THE PRODUCTION OF IMPROVED CELLULOSIC PRODUCTS WHICH COMPRISES MODIFYING A VISCOSE BY INCORPORATING THEREIN A POLYALKYLENE GLYCOL HAVING AN AVERAGE MOLECULAR WEIGHT OF AT LEAST ABOUT 400 AND AN HYDROXY FATTY ACID, AND EXTRUDING THE RESULTANT VISCOSE INTO AN ACID SPIN BATH. 